These options will be used on objects of class 'grouped_df'.
opts_grouped_df(constructor = c("default", "next", "list"), ...)An object of class <constructive_options/constructive_options_factor>
Depending on constructor, we construct the object as follows:
"next" : Use the constructor for the next supported class. Call .class2()
on the object to see in which order the methods will be tried.
"list" : We define as an list object and repair attributes.